Blood group substances A, B, O(H), Lea and Leb, are genetically determined antigens found on red cell surfaces and as water-soluble components in secretions of Secretors. The serological specificity resides in the carbohydrate moiety of these glycoprotein- and glycolipid-antigens. It is proposed to use two methods recently developed in our laboratories to cleave the oligosaccharides at the carbohydrate-protein linkage area. The quantitative borotritiide Beta-elimination procedure will be adapted to the detection and quantitation of the different types of oligosaccharides to be found in the blood group substances and other biologically active glycoproteins, and used to correlate structure with specificity. On the other hand, the use of the purified alpha-N-acetylgalactosaminyl-oligosaccharase on these same glycoproteins will enable the cleavage of the glycoproteins at the carbohydrate-protein linkage area to yield the two moieties essentially intact and undegraded. Under these conditions it will be possible to assess the contribution of each component, carbohydrate and protein, to the overall biological properties of the original glycoprotein. Presence of sialic acid residues on the erythrocyte surface is vital for the maintenance of erythrocytes in circulation. We propose to investigate the mechanism involved in the elimination of asialo-erythrocytes from the circulation and ascertain its role in the elimination of senescent erythrocytes as a normal physiological function. The significance of these studies to hematological disorders involving red blood cells is under investigation.